R package sansSouci: Post hoc inference via multiple testing. The goal of sansSouci is to perform post hoc inference: in a multiple testing context, sansSouci provides statistical guarantees on possibly user-defined and/or data-driven sets of hypotheses. Typical use cases include: Differential gene expression studies in genomics: see differential expression vignette and run volcano plot shiny app fMRI studies in neuroimaging: see fMRI vignette. In both cases, the permutation-based post hoc inference methods implemented in the SansSouci package outperform classical post hoc bounds based on probabilistic inequalities.